Microfibril

Cellulose is synthesized by cellulose synthase or Rosette terminal complexes which reside on a cells membrane. As cellulose fibrils are synthesized and grow extracellularly they push up against neighboring cells. Since the neighboring cell can not move easily the Rosette complex is instead pushed around the cell through the fluid phospholipid membrane. Eventually this results in the cell becoming wrapped in a microfibril layer. This layer becomes the cell wall. The organization of microfibrils forming the primary cell wall is rather disorganized. However, another mechanism is used in secondary cell walls leading to its organization. Essentially, lanes on the secondary cell wall are built with microtubules. These lanes force microfibrils to remain in a certain area while they wrap. During this process microtubules can spontaneously depolymerize and repolymerize in a different orientation. This leads to a different direction in which the cell continues getting wrapped.

Fibrillin microfibrils are found in connective tissues, which mainly makes up fibrillin-1^[1] and provides elasticity. During the assembly, mirofibrils exhibit a repeating stringed-beads arrangement produced by the cross-linking of molecules forming a striated pattern with a given periodicity when viewed stained under an electron microscope. In the formation of elastic fiber, fibrillin microfibrils guides the deposit of tropoelastin and remains in the outer layer of mature elastin fibers.^[2] The microfibril is also associated in cell communication. Formation of fibrillin microfibrils in the pericellular region affects the activity of a growth factor called TGFβ.^[1]

In Marfan syndrome, a connective tissue disorder, mutations in the gene encoding for the fibrillin-1 protein impact nearly every one of its domains.^[3] Such defects in fibrillin-1 affect the signaling of TGFβ, as microfibrils directly govern the activity of TGFβ.^[1] This hinders the formation of the extracellular matrix, and ultimately results in a severe phenotype which involves a few organ systems, including the central nervous system, circulatory system, ocular system, and skeletal system.^[4]

• Fibril